Process for dehydration of mono-alcohol(s) using a modified crystalline aluminosilicate

ABSTRACT

The invention relates to a process for dehydration of a mono-alcohol, or of a mixture of at least two mono-alcohols, having at least 2 carbon atoms and at most 7 carbon atoms into olefins having the same number of carbons, wherein the process uses a catalyst composition that comprises a modified crystalline aluminosilicate has an acidity between 350 and 500 μmol/g that comprises, and further wherein the catalyst composition is obtained by a process comprising the steps of providing a crystalline aluminosilicate having a Si/Al framework molar ratio greater than 10; and steaming said crystalline aluminosilicate, or said shaped and/or calcined crystalline aluminosilicate at a temperature ranging from 100° C. to 380° C.; and under a gas phase atmosphere, without liquid, containing from 5 wt % to 100 wt % of steam; at a pressure ranging from 2 to 200 bars; at a partial pressure of H 2 O from 2 bars to 200 bars; and said steaming being performed during at least 30 min and up to 144 h.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of PCT/EP2017/072294 filed Sep. 6,2017, which claims priority from EP 16290172.2 filed Sep. 9, 2016, whichare incorporated herein by reference in their entireties for allpurposes.

TECHNICAL FIELD

The present invention relates generally to the field of dehydration andskeletal isomerization of alcohols on acidic catalysts to makecorresponding olefins, preferably of alcohols having at least fourcarbon atoms for the production of olefins having the same number ofcarbon atoms as the alcohols. The present invention relates to acatalyst composition comprising a modified crystalline aluminosilicatepreferably of the group FER (Framework Type FER) or SZR and to a processfor the preparation thereof. The present invention also relates to theuse of said catalyst composition in a dehydration process of alcoholsand to the use of the olefins so-produced in various subsequentprocesses.

BACKGROUND OF THE INVENTION

The dehydration reactions of alcohols to produce alkenes have been knownfor a long time. Solid acid catalysts are widely used for alcoholdehydration and the conversion of alcohols therewith is nearly complete.However, in view of the potential downstream applications of olefins, itis of particular importance to limit the amount of secondary productsand ensure a stable catalyst performance to gain in process efficiencyand to save expensive steps of downstream separation/purification aswell as to recover the catalyst activity by regeneration. Zeolites-basedcatalysts are particularly interesting for alcohols dehydration due totheir high-activity, high-yield of corresponding olefins, and apossibility to operate under high-pressure conditions, which offers thebest energy efficiency solutions for the technology.

Dehydration of ethanol on zeolites was described in WO2011/089235. Theprocess for the dehydration of ethanol to ethylene was carried out inpresence of zeolite catalysts and provides an alternative route toethylene from biobased products if ethanol is obtained by fermentationof carbohydrates.

Dehydration of isobutanol to the corresponding olefins brings aperspective route to produce the renewable feedstock for petrochemicalsand refining applications. Unfortunately, the direct conversion ofisobutanol over a conventional dehydration catalyst, for example onalumina, leads to a product rich in isobutene. Selective production oflinear butenes from iBuOH requires again a zeolite-based catalyst. Thecut that is rich in linear butenes is often interesting as feedstock formetathesis, sulfuric acid catalyzed alkylation, oligomerization,oxidative dehydrogenation to butadiene, for the use as a copolymer.Therefore, the efficient catalyst for one-pot process convertingisobutanol to the effluent rich in the linear butenes is sought.

While many skeletal isomerization catalysts for the conversion ofn-butenes into isobutene have been developed, the reverse skeletalisomerization of isobutene into n-butenes has been rarely mentioned.Among the catalysts being active and selective, there are mostlyunidirectional 10-membered ring zeolites. WO2011/113834 relates to thesimultaneous dehydration and skeletal isomerization of isobutanol onacid catalysts. The process discloses the contact of a stream comprisingisobutanol with a catalyst able to make such reaction. The catalyst wasa crystalline silicate, a dealuminated crystalline silicate, orphosphorus modified crystalline silicate having Si/Al higher than 10; orsilicoaluminaphosphate molecular sieve, or a silicated, zirconated ortitanated or fluorinated alumina. The conversion of isobutanol wasalmost complete with selectivity in butenes ranging from 95 wt % to 98wt %. The selectivity in isobutene was around 41-43%. This documentindicates that steaming at temperatures above 400° C. leads to amodification of the acidity of the catalyst and to the removal ofaluminium from the crystalline silicate framework. Subsequently, it isnecessary to treat the catalyst via a leaching to remove the aluminiumand to increase the ratio Si/Al. The steps of steaming and leaching areassociated in this document.

However, crystalline silicate catalysts deactivate fast and have limitedregenerability. Hence, there is still a need for selective catalyststowards linear olefins and having improved regenerability.

In catalysis letters 41 (1996) 189-194, Gon Seo et al. studied theimpact of coke deposits on ferrierite zeolites for the reaction ofskeletal isomerization of 1-butene. The ferrierite studied was calcinedat 500° C. for 16 h without any other particular treatment aiming atmodifying its acidity. This ferrierite has a Si/Al ratio of 21 and it isfurther covered with coke using a plasma deposition before the reactionof skeletal isomerization of 1-butene is studied.

In WO2013/014081, SUZ-4 is studied for the methanol to olefin reaction.This document discloses the possibility of steaming the catalyst at atemperature of at least 400° C. followed by a leaching, i.e. a washing,of the steamed solid with an aqueous acid solution. Such treatment issaid to increase the Si/Al ratio.

In Applied Catalysis A: General 208 (2001) 153-161, Rutenbeck et al.studied the skeletal isomerization of n-butenes to isobutene. Thecatalyst studied was a ferrierite having a Si/Al ratio in the range of20-70. A treatment of the ferrierite with the inorganic acid HCl wasperformed to obtain the protonic form of the ferrierite.

In the Journal of Catalysis 163, 232-244 (1996), Wen-Qing Xu et al.studied the modification ferrierite for the skeletal isomerization ofn-butene. The ferrrierite used presents a Si/Al ratio of 8.8. Treatmentof the ferrierite also includes steaming at a temperature of at least550° C. and acidic treatment with HCl or HNO₃.

In EP2348005, the use of a ferrierite based catalyst for the dehydrationof isobutanol is described. It is disclosed that the ferrierite may beused directly without further treatment or that it may be used oncebeing steamed and dealuminated with an acidic treatment.

In Applied Catalysis A: General 403 (2011) 1-11, Dazhi Zhang et al. isdescribed the use of a ferrierite for the conversion of n-butanol toiso-butene. Such ferrierite was calcined at 550° C. but did not undergoany further treatment.

In U.S. Pat. No. 5,523,510, the use of an acid wash ferrierite basedcatalyst for the skeletal isomerization of n-olefins to iso-olefins isdescribed. Such acid wash is performed with HCl. In all the examples,the ferrierite is firstly steamed above 400° C. at atmospheric pressurebefore being acid washed.

In EP 0 134 333, a method of preparation of a cracking catalystcomprising a zeolite with a Si/Al ratio of at least 250 with a binder isdescribed.

In EP 0 034 444, a method for increasing the catalytic of acid zeolitecatalyst is described.

To summarize, zeolite-based catalysts are important for alcoholsdehydration, skeletal isomerization of butenes, MTO and many otherreactions. To tune the Si/Al ratio of zeolite, dealumination viasteaming at a temperature above 400° C. under atmospheric pressurefollowed by a leaching is usually performed. However, such treatmentleads to the formation of extra framework aluminium and partialdestruction of the zeolite framework that induce different diffusionproperties. Consequently, the selectivity of a catalyst prepared with asteamed and leached zeolite is generally impacted by the steaming. Inthe particular case of FER and SZR (SUZ-4), steaming followed byleaching has an even stronger impact on the selectivity due to theplate-shaped crystal morphology of those frameworks. However, FER andSZR are interesting because of their very high selectivity.Additionally, those structure types are particularly difficult tosynthesize with a Si/Al atomic ratio above 35. Tuning of the acidity isconsequently not easy albeit necessary. The present invention aims atproviding catalyst compositions that address the above-discusseddrawbacks of the prior art and solve the problem.

SUMMARY OF THE INVENTION

In particular, it is an object of the present invention to provide aprocess for dehydration of a mono-alcohol, or of a mixture of at leasttwo mono-alcohols using a catalyst based on modified crystallinealuminosilicate or zeolite (both terms are equivalent) being preferablyof the Framework Type FER or SZR and having a Si/Al framework molarratio greater than 10 exhibiting substantially complete once-throughconversion of the C2-C7 alcohols to the corresponding olefins.

In a preferred mode, the present invention provides a catalyst showinggood to excellent selectivity to linear olefins, above thermodynamicequilibrium, in simultaneous dehydration and skeletal isomerizationreaction of alcohols having at least four carbon atoms.

In one aspect of the present invention, a process for modifying acrystalline aluminosilicate is provided as well as a modifiedcrystalline aluminosilicate obtained by said process. Said modifiedcrystalline aluminosilicate is for instance useful for the preparationof a catalyst that can be used in the conversion of the C2-C7 alcoholsto the corresponding olefins. In a preferred mode said modifiedcrystalline aluminosilicate is particularly useful for the simultaneousdehydration and skeletal isomerization of a mono-alcohol having at leastfour carbon atoms into olefins having the same number of carbons. In amost preferred application, said mono-alcohol is isobutanol, i.e. 2methyl propan-1-ol.

According to a first aspect, the invention provides a process fordehydration of a mono-alcohol, or of a mixture of at least twomono-alcohols, having at least 2 carbon atoms and at most 7 carbon atomsinto olefins having the same number of carbons, the process comprisingthe following steps:

-   -   i.) providing a catalyst composition;    -   ii.) providing a feed (A) comprising said mono-alcohol, or said        mixture of at least two mono-alcohols, optionally water,        optionally an inert component;    -   iii.) contacting said feed (A) with said catalyst at conditions        effective to dehydrate at least a portion of said mono-alcohol;    -   iv.) recovering an effluent (B) and removing water, the inert        component if any and unconverted alcohols if any to get said        olefins having the same number of carbons as said mono-alcohol        the process being remarkable in that said catalyst composition        comprises a modified crystalline aluminosilicate has an acidity        between 350 and 500 μmol/g measured by temperature programmed        desorption of ammonia, wherein catalyst composition is obtained        by a process comprising the following steps:    -   a) providing a crystalline aluminosilicate having a Si/Al        framework molar ratio greater than 10;    -   b) optionally shaping and/or calcining said crystalline        aluminosilicate;    -   c) steaming said crystalline aluminosilicate, or said shaped        and/or calcined crystalline aluminosilicate:        -   at a temperature ranging from 100° C. to 380° C.; and        -   under a gas phase atmosphere, without liquid, containing            from 5 wt % to 100 wt % of steam the rest being one or more            gas selected from N₂, CO₂, Ar, He, CH₄, air, or any mixture            of thereof; with preference air is selected from air and            depleted air containing below 10 wt % of oxygen as based on            the total weight of the depleted air, preferably below 5 wt            %, more preferably below 1 wt %; and        -   at a pressure ranging from 2 to 200 bars; and        -   at a partial pressure of H₂O from 2 bars to 200 bars; and    -   said steaming being performed during at least 30 min and up to        144 h.        The content of steam in wt % is based on the total weight of the        gas phase atmosphere.

The process for modifying a crystalline aluminosilicate avoids theformation of the defects in the crystalline aluminosilicate, it avoidsblocking the porosity simultaneously to a decrease of the effectivenumber of the acid sites. Indeed, it has been discovered that a mildsteaming, i.e. steaming performed at a maximum temperature of 380° C.and under pressure, i.e. a pressure higher than the atmospheric pressureis particularly beneficial for the activity, selectivity andregenerability of the catalyst prepared with said modified crystallinealuminosilicate. It has been particularly discovered that modifiedcrystalline aluminosilicate being prepared according to theabove-mentioned recipe presents acidic properties that are particularlysuitable for the dehydration of mono-alcohol or of mixture of alcoholshaving 2 to 7 carbon atoms as well as for the simultaneous dehydrationand skeletal isomerization of a mono-alcohol(s) into olefins having thesame number of carbons. Such modified crystalline aluminosilicate has asufficient acidity to perform the dehydration reaction with a goodactivity while not being too acidic thereby maintaining a suitableselectivity toward normal olefins. Said modified crystallinealuminosilicate is therefore particularly useful for instance in thepreparation of a catalyst that can be used for alcohol dehydration intocorresponding olefins having the same number of carbons saidmono-alcohol being preferably ethanol, isobutanol, i.e. 2 methylpropan-1-ol.

With preference, one or more of the following features can be used tobetter define the inventive process for modifying a crystallinealuminosilicate:

-   -   The step c) of steaming said crystalline aluminosilicate is        performed at a temperature of at least 200° C., preferably at        least 250° C.    -   The step c) of steaming said crystalline aluminosilicate is        performed a temperature of at most 350° C.    -   The step c) of steaming said crystalline aluminosilicate is        performed at a pressure ranging from 2 to 20 bars, more        preferably ranging from 2 to 15 bars.    -   The step c) of steaming said crystalline aluminosilicate is        performed at a partial pressure of H₂O from 3 to 10 bars.    -   No any leaching treatment is performed either before step a) or        after step c) in order to maintain constant the concentration of        aluminium in the modified crystalline aluminosilicate;    -   A step of washing or ion exchange with for instance an alkali        metal or NH₄ salts is performed after step c) or before step b).    -   A calcination step of the product obtained after step c) or        before step b) is performed.    -   An step of recovering said modified crystalline aluminosilicate        is performed after c) or after any of the other optional steps.    -   The modified crystalline aluminosilicate is a 10 membered ring        zeolite preferably of the Framework Type FER, MWW, EUO, MFS,        ZSM-48, MTT, MFI, MEL, TON or SZR and is preferably chosen among        ferrierite, FU-9, ISI-6, NU-23, Sr-D, ZSM-35, ZSM-57 or SUZ-4 or        any mixture thereof.    -   The modified crystalline aluminosilicate has Si/Al framework        molar ratio ranging from 10 to 100, preferably ranging from 10        to 65, more preferably from 20 to 50, more preferably ranging        from 21 to 30.    -   The modified crystalline aluminosilicate has a content in        transition metals or cations thereof lower than 1000 ppmwt,        preferably measured by the method ASTM UOP961-12, said        transition metals belonging to any of the columns 3 to 12 of the        Periodic Table. Indeed, transition metals or cations thereof are        particularly detrimental for the catalyst selectivity because        they catalyze the formation of heavy hydrocarbons.    -   The modified crystalline aluminosilicate obtained by said        process for modifying a crystalline aluminosilicate has an        acidity between 350 and 525 μmol/g preferably between 400 and        500 μmol/g measured by temperature programmed desorption of        ammonia.    -   The process for modifying a crystalline aluminosilicate is        remarkable in that said crystalline aluminosilicate is shaped        (μ-spheres by spray-drying or droplet, tablets, extrudates:        trilobes, quadrilobes, cylinders) preferably in quadrilobes        extrudates prior to any of steps a) to c) with a binder being        preferably a silicic binder, AlPO₄, clay, a zirconia, or a        titania oxide more preferably being silica, SiO₂, i.e. said        binder contains at least 99.5% of SiO₂ with a maximum        concentration of aluminium, gallium, boron, iron and/or chromium        of 1000 ppm wt, preferably 500 ppm wt, more preferably 200 ppm        wt.    -   Said crystalline aluminosilicate is shaped or extruded prior to        any of steps a) to c) with a binder selected from AlPO₄, clay,        zirconia, titania oxide or silica, more preferably the binder        comprises or is silica.    -   The process for modifying a crystalline aluminosilicate is        remarkable in that preferably after step c) a further step of        shaping or extruded preferably in quadrilobes is performed with        a binder being preferably a silicic binder, AlPO₄, clay, a        zirconia, or a titania oxide more preferably being silica, SiO₂,        i.e. said binder contains at least 99.5% of SiO₂ with a maximum        concentration of aluminium, gallium, boron, iron and/or chromium        of 1000 ppm wt, preferably 500 ppm wt, more preferably 200 ppm        wt.    -   The product obtained after step c) is further shaped or extruded        with a binder selected from AlPO₄, clay, zirconia, titania oxide        or silica, preferably the binder comprises or is silica.    -   The binder is selected to comprise at least 85 wt % of silica as        based on the total weight of the binder, preferably at least        99.5 wt %.    -   The binder is selected to comprise less than 1000 ppm by weight        as based on the total weight of the binder of aluminium,        gallium, boron, iron and/or chromium, preferably less than 500        wt ppm, more preferably less than 200 wt ppm.    -   Said steaming of step c) is performed on a shaped or extruded        crystalline aluminosilicate in situ prior to step iii.) of said        process for dehydration of a mono-alcohol to obtain said        catalyst.    -   The process for modifying a crystalline aluminosilicate is        further remarkable in that preferably neither any steaming at a        temperature higher than 380° C. nor any leaching has been        performed on said crystalline aluminosilicate prior to being        used for instance in the dehydration of a mono-alcohol into        olefins having the same number of carbons.    -   The process for modifying a crystalline aluminosilicate is        further remarkable in that it is a versatile process: it can be        performed in situ or ex situ. Said process for modifying a        crystalline aluminosilicate can preferably be performed on a        catalyst comprising the crystalline aluminosilicate to be        modified. Said process for modifying a crystalline        aluminosilicate can more preferably be performed on a catalyst        comprising the crystalline aluminosilicate to be modified        already loaded and prior to its use for instance in a process        for dehydration of a mono-alcohol. Alternatively said process        for modifying a crystalline aluminosilicate can be performed on        the crystalline aluminosilicate to be modified prior to its        incorporation and/or prior to the shaping into a catalyst.    -   The process for dehydrating a mono-alcohol, or of a mixture of        at least two mono-alcohols, is further remarkable in that said        conditions effective to the simultaneous dehydration and        skeletal isomerization of a mono-alcohol into olefins having the        same number of carbons are any combinations of:        -   Adiabatic or isotherm operating conditions or any of            intermediate conditions in between the adiabatic and the            isotherm including for instance partial heat compensation or            intermediate re heating; and/or        -   An inlet temperature ranging from 200° C. to 500° C.,            preferably 225° C. to 450° C., most preferably 250° C. to            400° C.; and/or        -   A pressure ranging from 0.5 bar to 15 bars absolute (50 kPa            to 1.5 MPa) preferably 0.5 bar to 10 bars absolute (50 kPa            to 1.0 MPa) most preferably 1.2 to 9 bars absolute (0.12 MPa            to 0.9 MPa); and/or        -   A Weight Hourly Space Velocity (WHSV) ranging from 1 to 30            h⁻¹ preferably from 2 to 21 h⁻¹, more preferably from 3 to 9            h⁻¹, wherein the WHSV represents the weight flow rate of            said mono-alcohol at the inlet of the reactor divided by the            mass of the catalyst in said reactor; and/or        -   Said feed (A) having a partial pressure of alcohols from 0.1            to 15 bars absolute (0.01 MPa to 1.5 MPa) more preferably            from 0.5 to 9 bars absolute (0.05 MPa to 0.9 MPa).    -   the process for dehydrating a mono-alcohol is further remarkable        in that said mono-alcohol(s) has at least four carbon atoms and        at most five carbon atoms and in that said dehydration of a        mono-alcohol is performed together with a skeletal isomerization    -   the process for dehydrating a mono-alcohol is further remarkable        in that said mono-alcohol is isobutanol, i.e. 2 methyl        propan-1-ol that is converted into n-butenes and isobutene

It has been discovered that said modified aluminosilicate areparticularly suitable for the dehydration of alcohols. In particular,the above described ranges of acidity are perfectly well suited forhaving a sufficient catalyst activity while maintaining the selectivityat a sufficient level.

The process for modifying a crystalline aluminosilicate is particularlyversatile. The steaming can be applied directly after the synthesis ofthe crystalline aluminosilicate or it can be applied once the catalysthas been shaped or extruded with a binder. Said process for modifying acrystalline aluminosilicate can also be performed in situ, i.e. once thecatalyst comprising a crystalline aluminosilicate is loaded in adehydration reactor or in the dehydration and skeletal isomerizationreactor, i.e. prior to its use. In this latter case there is no need tohave a dedicated unit to perform the steaming under pressure. Catalystmanufacturers do not necessarily have the facilities to perform asteaming under pressure, but it is still possible to prepare saidmodified crystalline aluminosilicate in situ of the dehydration andoptionally isomerization unit.

Additionally, it has been discovered that the process for modifying analuminosilicate leads to improved properties. Without willing to bebound by any theory, it is assumed that a low temperature steamingassociated with an increase partial pressure during the steaming and theabsence of any leaching is particular beneficial for the activity andselectivity of the modified crystalline aluminosilicate. Therefore tomaintain the good activity and selectivity, any further steaming at ahigh temperature or any further leaching should be avoided.

DETAILED DESCRIPTION OF THE INVENTION

The terms “catalyst” and “catalyst composition” are used interchangeablyand refer to a composition comprising a crystalline aluminosilicate anda binder. According to the invention, the catalyst compositioncomprising a modified crystalline aluminosilicate comprises a binder,preferably an inorganic binder. The catalyst composition comprises from5 to 95 wt % as based on the total weight of the catalyst of crystallinealuminosilicate, preferably from 10 to 90 wt %, more preferably at least20 to 80 wt % even more preferably from 30 to 70 wt %.

In a preferred embodiment, the crystalline aluminosilicate or themodified crystalline aluminosilicate of the Framework Type FER is acrystalline aluminosilicate containing advantageously at least one10-membered ring into the structure based on T-atoms, i.e. on the Al andSi atoms contained in said ring. The family of Framework Type FERincludes Ferrierite, [B—Si—O]-FER, [Ga—Si—O]-FER, [Si—O]-FER,[Si—O]-FER, FU-9, ISI-6, Monoclinic ferrierite, NU-23, Sr-D, ZSM-35, andSUZ-4. Preferably, the modified crystalline aluminosilicate of theFramework Type FER is Ferrierite. The process for modifying acrystalline aluminosilicate does not change the Framework Type FER.

The Si/Al framework molar ratio of the modified crystallinealuminosilicate may be at least 11, preferably at least 15, morepreferably at least 20, even more preferably at least 21, mostpreferably at least 22, and even most preferably at least 25.Preferably, the Si/Al framework molar ratio of the modified crystallinealuminosilicate may be at most 150, preferably at most 100, morepreferably at most 75, even more preferably at most 65, most preferablyat most 55 and even most preferably at most 35. In a preferredembodiment, the Si/Al framework molar ratio of the modified crystallinealuminosilicate may range from 11 to 150, preferably from 15 to 100,more preferably from 20 to 100, even more preferably from 20 to 75, andin particular from 25 to 35. In a preferred embodiment, the Si/Alframework molar ratio of the modified crystalline aluminosilicate isranging from 10 to 65. Advantageously the modified crystallinealuminosilicate shows a high crystallinity of its zeolite phase, saidcrystallinity being similar to the crystallinity of the parent zeolitebefore modification, i.e. said crystallinity is similar to thecrystallinity of the crystalline aluminosilicate before being modified.A similar crystallinity is evidenced via the X ray diffraction patterns(less than 20% of difference measured on the area below the X raycurves), i.e. the X ray diffraction pattern of the crystallinealuminosilicate (before being modified) is the same as the crystallinityof the modified crystalline aluminosilicate.

In a preferred embodiment, said modified crystalline aluminosilicate hascontent in redox transition metals or cations thereof lower than 1000ppm wt, said transition metals belonging to one of the columns 3 to 12of the Periodic Table. Preferably, said metals are Fe, Co, Ni, Cu, Mo,Mn, Ti, Zn, V, Cr, Ru, Rh, Cd, Pt, Pd, Au, Zr. Preferably, said modifiedcrystalline aluminosilicate has content in metals or cations thereof asdefined above lower than 500 ppm wt, more preferably lower than 200 ppmwt, most preferably lower than 100 ppm wt, in particular lower than 50ppm wt being for instance measured by the method ASTM UOP961-12.

In another specific embodiment, the catalyst comprising a modifiedcrystalline aluminosilicate may comprise a binder, preferably aninorganic binder. The binder is selected so as to be resistant to thetemperature and other conditions employed in the dehydration process ofthe invention. The binder is an inorganic material selected from clays,silica, metal silicate, metal oxides (such as ZrO₂), aluminophosphatebinders, in particularly, stoichiometric amorphous aluminophosphate orgels including mixtures of silica and metal oxides. It is desirable toprovide a catalyst having good crush strength. This is because, incommercial use, it is desirable to prevent the catalyst from breakingdown into powder-like materials. Such clay or oxide binders have beenemployed normally only for the purpose of improving the crush strengthof the catalyst. Preferably, said binder is selected from the groupconsisting of clays, silica, titania, aluminophosphate, titania-silica.A particularly preferred binder for the catalyst composition of thepresent invention is silica. The relative proportions of the finelydivided modified crystalline aluminosilicate material and the inorganicoxide matrix of the binder can vary widely. Typically, the bindercontent may range from 5 to 95% by weight, more typically from 20 to 85%by weight, based on the weight of the catalyst composition. By adding abinder to the catalyst composition, this latter may be formulated intopellets, extruded into other shapes, or formed into spheres or aspray-dried powder. The binder is preferably selected to comprise atleast 85 wt % of silica as based on the total weight of the binder,preferably at least 90 wt %, more preferably at least 95 wt % even morepreferably at least 99 wt % and most preferably at least 99.5 wt %. Thebinder is preferably selected to comprise less than 1000 ppm by weightas based on the total weight of the binder of aluminium, gallium, boron,iron and/or chromium, preferably less than 500 wt ppm, more preferablyless than 200 wt ppm.

The modified crystalline aluminosilicate may be in H-form. The H-form ofa modified crystalline aluminosilicate of the Framework Type FER meansthat it comprises oxygen atoms bonded to one aluminium atom and onesilicon atom, and which is protonated with a hydrogen atom, resulting inthe following sequence —[—Al—O(H)—Si—]—. In the present invention, themodified crystalline aluminosilicate may be essentially under H-form,which means containing less than 1000 ppmwt of the total amount of thealkali ions and the alkaline earth ions. In another embodiment, themodified crystalline aluminosilicate is partly under H-form. It meansthat in said modified crystalline aluminosilicate part of the hydrogenatoms bonded to oxygen atoms in the following sequence —[—Al—O(H)—Si—]—is substituted by metallic ions, preferably alkali ions, alkaline earthions or silver ions. Preferably, the alkali ions or alkaline earth ionsmay be Na, K, Cs, Li, Mg or Ca being measured via chemical analysis withfor instance the method ASTM UOP961-12.

Said process for modifying a crystalline aluminosilicate is particularlyremarkable in that, preferably, no leaching is performed. The termleaching shall encompass any treatment of a solid with an acidic medium(inorganic or organic) or complexing agent able to remove aluminium fromthe crystalline aluminosilicate framework or preferably extra frameworkaluminium (EFAL).

As non-limiting example, said acidic medium and/or said complexing agentused in leaching treatment shall encompass citric acid, formic acid,oxalic acid, tartaric acid, malonic acid, succinic acid, glutaric acid,adipic acid, maleic acid, phthalic acid, isophthalic acid, fumaric acid,nitrilotriacetic acid, hydroxyl ethylene diamine triacetic acid,ethylene diamine tetraacetic acid, trichloroacetic acid, trifluoroaceticacid, methansulfonic or a salt of such an acid (e.g. the sodium salt) ora mixture of two or more of such acids or salts. Inorganic acids, suchas nitric acids or halogenic acids, are also encompassed in the meaningof acidic medium. Complexing agent shall encompass any organic moleculeable to form a complex with aluminium and preferably forms awater-soluble complex with aluminium in order to remove aluminium andpreferably extra framework aluminium (EFAL). A particularly preferredcomplexing agent may comprise an amine, preferably ethylene diaminetetraacetic acid (EDTA) or a salt thereof, in particular the sodium saltthereof. The term complexing agent shall encompass also organic acidicmedium but not only. The person skilled in the art can recognize theorganic medium able to remove the aluminium or EFAL from a crystallinealuminosilicate. As a guidance, it may be put forward that said organicmedium refers to organic molecules able to form a complex with aluminiumand preferably forms a water-soluble complex with aluminium in order toremove aluminium or EFAL, i.e. in order to remove at least 5 wt %preferably 10 wt % of the aluminium or EFAL present on the crystallinealuminosilicate. It shall also be clear that said modified crystallinealuminosilicate is not preferably further leached prior to its use forinstance in the process for dehydrating mono-alcohols.

In an optional embodiment, the process for modifying a crystallinealuminosilicate encompasses an optional calcinations. Said calcinationsare performed to burn organic component that may be present on thecrystalline aluminosilicate but under conditions avoiding the formationof pentahedral aluminium. In particular, at the inlet of thecalcinations reactor, the calcination gas should contain less than 1000ppmwt of water. Therefore, even if the crystalline aluminosilicatecontains interstitial water, the presence of water inside thecalcinations reactor is low enough to avoid a partial steaming of thecrystalline aluminosilicate. During the optional calcinations, thecrystalline aluminosilicate may be under the NH₄ form, the Na, K orH-forms. The calcinations can be performed under atmospheric pressure oralternatively at a pressure up to 9 bars. The calcination gas maycontain inert components such as for instance N₂, Ar, He, CO₂, or otherspecies such as for instance natural gas components or CO, N₂O which arenot inert under the calcination conditions but do not lead to thedeposition of any molecules such as coke on the crystallinealuminosilicate. The calcinations may be alternatively be performedunder depleted air or the calcination gas may contains below 10 wt % ofoxygen or preferably below 5 wt % or even below 1 wt % of oxygen, asbased on the total weight of the depleted air, in order to avoid thethermal runaway when organic molecules are burnt during calcinations.Indeed, in depleted air the content of oxygen is based on the totalweight of said depleted air. The optional calcinations can be performedat a temperature not higher than 600° C., preferably 550° C., mostpreferably 500° C., and with a temperature increase of less than 10°C./min, preferably less than 1° C./min, the most preferably at 0.5°C./min, for a period of at least 30 min, preferably at least 2 h and atmost 48 h and under a gas flow containing at most 1000 ppm volume ofwater measured at the inlet of the calcination reactor. The optionalcalcinations can either be performed in situ or ex situ, i.e.calcinations can be applied directly after the synthesis of thecrystalline aluminosilicate or after the process for modifying thecrystalline aluminosilicate or it can be applied once the catalyst hasbeen shaped or extruded with a binder. Said optional calcinations canalso be performed in situ, i.e. once the catalyst comprising acrystalline aluminosilicate or a modified crystalline aluminosilicate isloaded in a dehydration reactor or in the dehydration and skeletalisomerization reactor, i.e. prior to its use in a process fordehydrating.

Preferably, the mono-alcohol or the mixture of at least twomono-alcohols have at least four carbon atoms and at most five carbonatoms. Said mono-alcohol is preferentially a primary mono-alcoholsubstituted by an alkyl group in position 2. Preferably, themono-alcohols are provided from biomass fermentation or biomassgasification to syngas followed by a modified Fischer-Tropsch synthesis.

Preferably, the alcohol(s) may be 1-butanol, 2-butanol, isobutanol,pentan-1-ol, 3-Methylbutan-1-ol, 2-Methylbutan-1-ol,2,2-Dimethylpropan-1-ol, pentan-3-ol, Pentan-2-ol, 3-Methylbutan-2-ol,2-Methylbutan-2-ol, or mixture thereof with the proviso that the mixturecontains alcohols having the same number of carbon atoms or optionallypresenting a different number of carbon atoms. For example, a mixture ofbutanol comprises two or more of the following alcohols: 1-butanol,2-butanol, isobutanol. A mixture of pentanol comprises two or more ofthe following alcohols: pentan-1-ol, 3-methylbutan-1-ol,2-methylbutan-1-ol, 2,2-dimethylpropan-1-ol, pentan-3-ol, pentan-2-ol,3-methylbutan-2-ol, 2-methylbutan-2-ol. More preferably, the alcohol maybe selected from C2-C4 alkyl substituted by one hydroxyl group ormixture thereof with the proviso that the alcohols contained in themixture have the same number of carbon atoms. Advantageously, theinvention is of interest for 1-butanol, 2-butanol, isobutanol or mixturethereof with the proviso that the mixture contains alcohols having thesame number of carbon atoms. In particular, a mixture of butanol isused, preferably isobutanol is used.

The dehydration reactor can be a fixed bed reactor (radial, isothermal,adiabatic etc), a moving bed reactor, multitubular or a fluidized bedreactor. A typical fluid bed reactor is one of the FCC type used forfluidized-bed catalytic cracking in the oil refinery. A typical movingbed reactor is of the continuous catalytic reforming type. Thedehydration may be performed continuously in a fixed bed reactorconfiguration using several reactors in series of equal or differentsizes or a pair of parallel “swing” reactors. The various preferredcatalysts of the present invention have been found to exhibit highstability. This enables the dehydration process to be performedcontinuously in two parallel “swing” reactors wherein when one reactoris operating, the other reactor is undergoing catalyst regeneration. Thecatalyst of the present invention also can be regenerated several times.

As preferred embodiment, the process for dehydration of a mono-alcoholor of a mixture of at least two mono-alcohols may be performed at apressure ranging from 0.5 to 30 bars absolute (50 kPa to 3 MPa),advantageously from 0.5 to 15 bars absolute (50 kPa to 1.5 MPa),advantageously from 0.5 to 10 bars absolute (50 kPa to 1 MPa).Advantageously, the partial pressure of the alcohol is lower than 5 barsabsolute (0.5 MPa) and more advantageously from 0.5 to 9 bars absolute(0.05 MPa to 0.9 MPa), preferably lower than 8 bars absolute (0.8 MPa)and more preferably lower than 7 bars absolute (0.7 MPa).

As preferred embodiment, the process for dehydration of a mono-alcoholor of a mixture of at least two mono-alcohols may be performed at atemperature ranging from 200° C. to 500° C., more advantageously from225° C. to 450° C. and preferably from 250° C. to 400° C. These reactiontemperatures refer mainly to the inlet temperature. Dehydration is anendothermic reaction and requires the input of reaction heat in order tomaintain catalyst activity sufficiently high and shift the thermodynamicequilibrium to sufficiently high conversion levels. In case of fluidisedbed reactors: (i) for stationary fluidised beds without catalystcirculation, the reaction temperature is substantially homogeneousthroughout the catalyst bed; (ii) in case of circulating fluidised bedswhere catalyst circulates between a converting reaction section and acatalyst regeneration section, depending on the degree of catalyst backmixing the temperature in the catalyst bed approaches homogeneousconditions (a lot of back mixing) or approaches plug flow conditions(nearly no back mixing) and hence a decreasing temperature profile willinstall as the conversion proceeds. In case of fixed bed or moving bedreactors, a decreasing temperature profile will install as theconversion of the alcohol proceeds. In order to compensate fortemperature drop and consequently decreasing catalyst activity orapproach to thermodynamic equilibrium, reaction heat can be introducedby using several catalyst beds in series with inter heating of thereactor effluent from the first bed to higher temperatures andintroducing the heated effluent in a second catalyst bed, etc. Whenfixed bed reactors are used, a multitubular reactor can be used wherethe catalyst is loaded in small-diameter tubes that are installed in areactor shell. At the shell side, a heating medium is introduced thatprovides the required reaction heat by heat-transfer through the wall ofthe reactor tubes to the catalyst.

As preferred embodiment, the process for dehydration of a mono-alcoholor of a mixture of at least two mono-alcohols may be performed with aweight hour space velocity ranging from 0.1 h−1 to 20 h−1, preferablyfrom 0.5 h−1 to 10 h−1, more preferably from 1 h−1 to 9 h−1. The WHSVrepresents the weight flow rate of the mono-alcohol at the inlet of thereactor divided by the mass of the catalyst in said reactor.

The effluent of the process for the simultaneous dehydration andskeletal isomerization comprises essentially water, olefin, an inertcomponent (if any) and unconverted mono-alcohol. Said unconvertedmono-alcohol is supposed to be as low as possible. The olefin isrecovered by usual fractionation means. Advantageously, the inertcomponent, if any, is recycled in the feed (A) as well as theunconverted alcohol, if any.

The inert components, if any, is any component provided that there is noadverse effect on the catalyst comprising the modified crystallinealuminosilicate. Dehydration of a mono-alcohol is an endothermicreaction; the inert component can be used to bring energy to thereactor. For instance, the inert components can be selected among water,saturated hydrocarbons having up to 10 carbon atoms, naphthenes,nitrogen and CO₂. An example of inert components can be any individualsaturated compound, a synthetic mixture of individual saturatedcompounds as well as some equilibrated refinery streams like straightnaphtha, butanes etc. Advantageously, it is a saturated hydrocarbon or amixture of saturated hydrocarbons having from 3 to 7 carbon atoms, moreadvantageously having from 4 to 6 carbon atoms and preferably pentane.The weight proportions of respectively alcohols, water and inertcomponent are, for instance, 5-100/0-95/0-95 the total being 100.

In a preferred embodiment, said process for dehydration of amono-alcohol or of a mixture of at least two mono-alcohols may furthercomprises a step of recovering and regenerating the catalyst.

In a preferred embodiment, at least 80% wt of the olefins obtained insaid process for dehydration of a mono-alcohol have the same number ofcarbon atoms as the mono-alcohol, preferably at least 85% wt, morepreferably at least 90% wt, in particular at least 95% wt.

In a preferred embodiment, the present process for dehydrating iscarried out with a mixture of butanol as mono-alcohol, preferablyisobutanol, and the mixture of olefins produced comprises at least 80%wt of butene and isomers thereof, preferably at least 90%, morepreferably at least 95% wt, most preferably at least 98% wt. Inaddition, the selectivity in n-butenes may be at least 65% wt based onthe total amount of butene and isomers thereof contained in the mixtureof olefins produced, preferably at least 70% wt.

In another aspect of the present invention, the mixture of olefinsproduced by the process for dehydration of a mono-alcohol may be used asstarting material for subsequent reactions such as the production ofpropylene via metathesis process, the production of butadiene viadehydrogenation, oligomerization, as well as for the production oftransportation fuels, monomers and fuel additives. The mixture ofolefins produced according to the present process may also replace theuse of raffinate as defined in U.S. Pat. No. 4,282,389 in the refineryor petrochemical plants. The most typical application of a mixturecontaining isobutene is the conversion of the said isobutene into ethers(MTBE and ETBE), into t-butylalcohol (TBA) or oligomers (e.g.di/tri-iso-butenes), all being gasoline components. The higher oligomersof isobutene can be used for jet fuel applications. High purityisobutene can further be made by the decomposition of ethers(backcracking) or TBA (dehydration). High purity isobutene findsapplications in the production of butyl-rubber, poly-isobutene,methylmethacrylate, isoprene, hydrocarbons resins, t-butyl-amine,alkyl-phenols and t-butyl-mercaptan. When the mixture of olefinscontains n-butenes which have not reacted during the production ofethers or TBA and substantially not or only to a limited extent duringthe oligomerisation, said n-butenes have applications in the productionof sec-butanol, alkylate (addition of isobutane to butenes),polygasoline, oxo-alcohols and propylene (metathesis with ethylene orself-metathesis between but-1-ene and but-2-ene). By means of superfractionation or extractive distillation or absorptive separationbut-1-ene can be isolated from the n-butenes mixture. But-1-ene is usedas comonomer for the production of polyethylenes, for polybut-1-ene andn-butyl-mercaptan. This involves an isomerization catalyst that islocated in the distillation column and continuously converts thebut-1-ene into but-2-ene, being a heavier component than but-1-ene.Doing so, a bottom product rich in but-2-ene and a top product poor inbut-1-ene and rich in isobutene is produced. The bottom product can beused as described above. One main application of such but-2-ene richstream is the metathesis with ethylene in order to produce propylene. Ifhigh purity iso-butene is desired the top product can be further superfractionated into substantially pure iso-butene and pure but-1-ene orthe isobutene can be isolated via formation of ethers or TBA that issubsequently decomposed into pure iso-butene. The n-butenes rich streammay be used for the production of butadiene via dehydrogenation oroxidative dehydrogenation or send to alkylation unit to producebio-alkylate. The mixture of isobutene and butenes can be sent to acatalytic cracking which is selective towards light olefins in theeffluent, the process comprising contacting said isobutene and butenesmixture with an appropriate catalyst to produce an effluent with anolefin content of lower molecular weight than that of the feedstock.Said cracking catalyst can be a silicalite (MFI or MEL type) or aP-ZSM5.

Analytical Methods

Measure of the acidity of the crystalline aluminosilicate or of themodified aluminosilicate can be performed by temperature desorption ofammonia. Method known in the art suitable to quantify the acidic sitescan be used. For instance, the method described in the procedure ASTMD4824-13 can be used. The amount of ammonia then determined via thismethod in cubic centimeter per grams can then be easily converted intoμmol/g.

Alternatively measure of the amount of acid sites can for instance bedone by temperature-programmed desorption of ammonia according thefollowing method. The temperature-programmed desorption of ammonia isperformed in a Pyrex®™ cell containing about 0.4 g of sample in form ofthe fraction 35-45 mesh. The cell is placed in an oven of the AUTOCHEMII 2920 equipped with TCD detector and the following steps are carriedout:

Activation:

this step is performed under a flow rate of dried (over molecular sievee.g. 3 A or 4 A) He of 50 cm³/min (<0.001% of water). The temperature isincreased from room temperature to 600° C. with a rate of 10° C./min.The temperature is then maintained at 600° C. during 1 h. Thetemperature is then decreased to 100° C. with a rate of 10° C./min.

Saturation:

this step is performed at 100° C. During a first hour, the solid is putin contact with a flow of 30 cm³/min of a dried (over molecular sievee.g. 3 A or 4 A, <0.001 of water) mixture of 10 weight % of NH₃ dilutedin He. Then, during the next 2 h, the solid is put in contact with aflow rate of 50 cm³/min of dried (over molecular sieve e.g. 3 A or 4 A,<0.001% of water) He to remove the physisorbed NH₃.

Analysis:

this step is performed under a flow of 50 cm³/min of dried (overmolecular sieve e.g. 3 A or 4 A, <0.001% of water) He. The temperatureis increased to 600° C. with a rate of 10° C./min. Once the temperatureof 600° C. has been reached, it is maintained for 1 h. The cell is thencooled down and weighted.

Calculation:

The amount of NH₃ desorbed from the solid is referenced to the weight ofthe sample by integrating the surface below the TCD curve and reportingto a calibration curve. The amount of NH₃ desorbed from the solid givesthe acidity of the solid in μmol/g.

Measure of the content of transition metals and determination of theSi/Al framework molar ratio in the catalyst, in the modified crystallinealuminosilicate or in the crystalline aluminosilicate can be done by anysuitable technique known in the art. For instance, it can be done usingthe method ASTM UOP961-12.

Alternatively measure of the Si/Al framework molar ratio in thecatalyst, in the modified crystalline aluminosilicate or in thecrystalline aluminosilicate can be determined using solid-state ²⁹Si MASNMR. All solid state ²⁹Si MAS MAS NMR spectra were recorded on a BrukerDRX500 spectrometer (Pulse 45°, Relaxation delay 7 sec, rotor 4 mm). Fora low defect zeolite samples, an aluminium atom will always besurrounded by four Silicones. The ²⁹Si MAS NMR spectra ofaluminosilicate zeolites give typically a series of peaks whichcorrespond to SiO₄ tetrahedra in five different possible environmentscorresponding to different numbers of AlO₄ tetrahedra connected to thesilicon via oxygen. For simplicity, these sites will be denoted ignoringthe oxygen atoms as Si (4-nAl), where n is a number of Si in thetetrahedral: Si(0Al), Si(1Al), Si(2Al), Si(3Al), Si(4Al). The intensityof a silicon resonance is proportional to the number of associatedsilicon atoms. The number of Al atoms is proportional to a sum of theeach corresponding peak multiplied by a number of Al (4-n) and divide by4. The intensity of each resonance is determined by deconvolution:Si(0Al), Si(1Al), Si(2Al), Si(3Al), Si(4Al).

The Si/Al ratio is then given by the following equation:Si/Al=4*Si total area/[Area Si(1Al)+2*Area Si(2Al)+3*Area Si(3Al)+4*AreaSi(4Al)]

EXAMPLES

The Si/Al framework molar ratio was determined using solid-state ²⁹SiMAS NMR measurement method described above.

The acidity was measured using the temperature-programmed desorption ofammonia method as described in the analytical methods above.

General procedure for dehydration process of alcohols is done asfollows: A stainless-steel reactor tube having an internal diameter of10 mm is used. 10 ml of the catalyst composition, as pellets of 35-45mesh, is loaded in the tubular reactor. The void spaces, before andafter the catalyst composition, are filled with SiC granulates of 2 mm.The temperature profile is monitored with the aid of a thermocouple wellplaced inside the reactor at the top of the catalyst bed. Before thereaction, the catalyst was pretreated in a nitrogen flow at 550° C. for2 h (heating rate 60° C./h) followed by cooling down to the reactiontemperature. The nitrogen is then replaced by the feed at the indicatedoperating conditions. The catalytic tests are performed down-flow, in apressure range from 1.5 to 11 bars, in a temperature range of 100−500°C. and with an alcohol weight hour space velocity varying from 0.1-20h⁻¹ (kg of product/hours×kg of catalyst). Analysis of the products isperformed by using an on-line gas chromatography.

Example 1

Sample A is made of FER55 (CP914 from Zeolyst international), extrudedwith SiO₂ (FER/SiO₂: 70/30). It is characterized by having a Si/Al inthe zeolite framework of 28 and an acidity of 750 μmol/g.

Example 2

Sample B has been obtained by steaming sample A with deionized water at300° C. at 8.8 bars during 24 h hours with a weight hour speed velocity(whsv) of 7.9 h−1 and under an atmosphere containing 100% of steam (i.e.at a partial pressure of H₂O of 8.8 bars). Sample B is characterized byhaving an acidity of 500 μmol/g.

Example 3

Sample C has been obtained by steaming sample A with deionized water at300° C. at 8.8 bars during 6 days with a weight hour speed velocity(whsv) of 7.9 h−1 and under an atmosphere containing 100% of steam (i.e.at a partial pressure of H₂O of 8.8 bars). Sample C is characterized byhaving an acidity of 400 μmol/g.

Example 4

Sample D has been obtained by steaming sample A with deionized water at350° C. at 8.8 bars during 24 hours with a weight hour speed velocity(whsv) of 7.9 h−1 and under an atmosphere containing 100% of steam (i.e.at a partial pressure of H₂O of 8.8 bars). Sample C is characterized byhaving an acidity of 425 μmol/g.

Example 5

Sample E has been obtained by steaming sample A according to a standardprocedure: steaming with deionized water at 600° C. under atmosphericpressure during 6 hours with a weight hour speed velocity (whsv) of 0.5h−1 and under an atmosphere containing 100% of steam. Sample E ischaracterized by having an acidity of 300 μmol/g.

Example 6

Sample F has been obtained by steaming sample A according to a standardprocedure: steaming with deionized water at 300° C. under atmosphericpressure during 24 hours with a weight hour speed velocity (whsv) of 7.9h−1 and under an atmosphere containing 100% of steam. Sample F ischaracterized by having an acidity of 550 μmol/g.

Example 7 (Comparison)

The catalysts described in the examples 1 to 5 have been crushed andsieved (35-45 mesh) for loading 10 mL in a fixed bed reactor. Thecatalysts are then subjected to isobutanol dehydration testing. Thetesting conditions are a pressure of 3 bars, a temperature between 250and 350° C. (isothermal) and an isobutanol weight hour space velocity(WHSV) of 7 h−1. Isobutanol was diluted with H2O, the ratioiBuOH/H2O=95/5. The results obtained at 300° C. and 350° C. arepresented in Table 1.

TABLE 1 Isobutanol dehydration test results under isothermal conditions.Reaction Temp.: 300° C. Reaction Temp.: 350° C. iBuOH C4 = nC4 = iBuOHC4 = nC4 = conv. sel. sel. conv. sel. sel. Sample A 100% 97.5% 80.5%100% 97.0% 73.0% (base) Sample B 100% 98.5% 82.0% 100% 97.5% 77.0%(invention) Sample C 100% 99.0% 83.5% 100% 98.5% 80.5% (invention)Sample D 100% 99.0% 86.0% 100% 99.0% 80.0% (invention) Sample E 87.0% 99.0% 75.0% 100% 98.0% 65.5% (comparative) Sample F 100% 97.0% 80.5%100% 97.0% 65.5% (comparative)

At a reaction temperature of 300° C. (Table 1), the catalysts treatedaccording the present invention have similar isobutanol conversion butimproved selectivity towards linear butenes compared to base catalyst(Sample A). The comparative sample E has lower conversion and lowerselectivity while comparative sample F is similar to base catalyst(Sample A)

At a reaction temperature of 350° C. (Table 1), the catalysts treatedaccording the present invention have similar isobutanol conversion butimproved selectivity towards linear butenes compared to base catalyst(Sample A) while the comparative samples E and F are much lessselective.

Example 8 (Comparison)

Sample A and sample B have been tested under adiabatic condition. Thetesting conditions are a pressure of 8.8 bars, an entrance temperatureof 350° C. (adiabatic) and an isobutanol weight hour space velocity(WHSV) of 7 h−1. For this test, 200 mL of extruded catalysts which wereblended with 200 ml of SiC are placed in 2 reactors (100 ml of catalystper reactor). The reactors were installed in a series with anintermediate reheating. The results obtained after 100 h on stream arepresented in Table 2.

TABLE 2 Isobutanol dehydration test results under adiabatic conditions.iBuOH conv. C4 = sel. nC4 = sel. Sample A (base) 99.5% 99.0% 78.0%Sample B (invention) 99.5% 99.0% 83.5%

According to testing results under adiabatic conditions (Table 2), thecatalysts treated according to the present invention have similarisobutanol conversion but improved selectivity towards linear butenescompared to base catalyst (Sample A).

Example 9 (Comparison)

Samples A, B and D have been loaded, in a 3 parallel fixed beds reactors(316L stainless steel, 13 mm internal diameter, downflow operating). 1.5g of extruded catalysts are diluted with 200 μm SiC. The catalyst isactivated under air (6NL/h) at 450° C. (10° C./min) during 1 h. Thecatalysts are then subjected to isobutanol dehydration testing underthese conditions: a pressure of 8.8 bars, a temperature of 300° C.(isothermal) and an isobutanol weight hour space velocity (WHSV) of 7h−1. Isobutanol was diluted with H2O, the ratio iBuOH/H2O=95/5 w/w. Theresults obtained in these conditions, after 50 h and after 300 h onstream, are presented here below (Table 3).

TABLE 3 Isobutanol dehydration test results under isothermal conditions(300° C.) at different time on stream. Time on stream: 50 h Time onstream: 300 h iBuOH C4 = nC4 = iBuOH C4 = nC4 = conv. sel. sel. conv.sel. sel. Sample A 100% 98.5% 83.5% 87.0% 99.5% 84.0% (base) Sample B100% 99.0% 85.0% 99.0% 99.5% 85.0% (invention) Sample D 100% 99.0% 85.0%99.0% 99.5% 85.0% (invention)

At a reaction temperature of 300° C., after 50 h on stream (Table 3,left part), the catalysts treated according the present invention havesimilar isobutanol conversion but improved selectivity towards linearbutenes compared to base catalyst (Sample A). At longer reaction time,at 300° C. (Table 3, right part), the isobutanol conversion obtainedwith base catalyst (Sample A) drops while samples prepared according tothe invention maintain high conversion. Furthermore, the catalyststreated according the present invention retain better selectivitytowards linear butenes and better stability compared to base catalyst(Sample A).

As shown in the present examples, the catalysts according to the presentinvention have several advantages compared to the catalysts known in theart.

The terms and descriptions used herein are set forth by way ofillustration only and are not meant as limitations. Those skilled in theart will recognize that many variations are possible within the spiritand scope of the invention as defined in the following claims, and theirequivalents, in which all terms are to be understood in their broadestpossible sense unless otherwise indicated. As a consequence, allmodifications and alterations will occur to others upon reading andunderstanding the previous description of the invention. In particular,dimensions, materials, and other parameters, given in the abovedescription may vary depending on the needs of the application.

The invention claimed is:
 1. A process for dehydration of amono-alcohol, or of a mixture of at least two mono-alcohols, having atleast 2 carbon atoms and at most 7 carbon atoms into olefins having thesame number of carbons, the process comprising the following steps: i.)providing a catalyst composition; ii.) providing a feed (A) comprisingsaid mono-alcohol, or said mixture of at least two mono-alcohols,optionally water, and optionally an inert component; iii.) contactingsaid feed (A) with said catalyst at conditions effective to dehydrate atleast a portion of said mono-alcohol and; iv.) recovering an effluent(B) and removing water, the inert component if any and unconvertedalcohols if any from said effluent (B) to recover said olefins havingthe same number of carbons as said mono-alcohol; characterized in thatsaid catalyst composition comprises a modified crystallinealuminosilicate having an acidity between 350 and 500 μmol/g measured bytemperature programmed desorption of ammonia, wherein said processfurther comprises a process for preparing said catalyst compositioncomprising the following steps: a) providing a crystallinealuminosilicate having a Si/Al framework molar ratio greater than 10; b)optionally shaping and/or calcining said crystalline aluminosilicate; c)steaming said crystalline aluminosilicate, or said shaped and/orcalcined crystalline aluminosilicate: at a temperature ranging from 100°C. to 380° C.; under a gas phase atmosphere, without liquid, containingfrom 5 wt % to 100 wt % of steam and the rest being one or more gasesselected from N₂, CO₂, Ar, He, CH₄, air, depleted air containing below10 wt % of oxygen as based on the total weight of the depleted air, orany mixture thereof; at a pressure ranging from 2 to 200 bars; at apartial pressure of H₂O from 2 bars to 200 bars; and said steaming beingperformed for a period at least 30 min and up to 144 h.
 2. The processfor dehydration of a mono-alcohol, or of a mixture of at least twomono-alcohols, according to claim 1, characterized in that the step c)of steaming said crystalline aluminosilicate is performed: at atemperature of at least 200° C.; and/or a temperature of at most 350°C.; and/or at a pressure ranging from 2 to 20 bars; and/or at a partialpressure of H₂O from 3 to 10 bars.
 3. The process for dehydration of amono-alcohol, or of a mixture of at least two mono-alcohols, accordingto claim 1, characterized in that said process for preparing saidcatalyst composition further comprises the following steps: notperforming any leaching treatment either before step b) or after step c)in order to maintain constant the concentration of aluminium in themodified crystalline aluminosilicate; performing an optional step ofwashing or ion exchange with an alkali metal or NH₄ salts after step c)or before step b); performing an optional calcination step of theproduct obtained after step c) or before step b); and/or performing anoptional step of recovering said modified crystalline aluminosilicateafter c).
 4. The process for dehydration of a mono-alcohol, or of amixture of at least two mono-alcohols, according to claim 1,characterized in that said crystalline aluminosilicate is a 10 memberedring zeolite of the Framework Type FER, MWW, EUO, MFS, ZSM-48, MTT, MFI,MEL, TON or SZR and is chosen among ferrierite, FU-9, ISI-6, NU-23,Sr-D, ZSM-35, ZSM-57 or SUZ-4 or any mixture thereof.
 5. The process fordehydration of a mono-alcohol, or of a mixture of at least twomono-alcohols, according to claim 1, characterized in that saidcrystalline aluminosilicate is shaped or extruded prior to any of stepsa) to c) with a binder selected from AlPO₄, clay, zirconia, titaniaoxide or silica.
 6. The process for dehydration of a mono-alcohol, or ofa mixture of at least two mono-alcohols, according to claim 5,characterized in that said steaming of step c) is performed on a shapedor extruded crystalline aluminosilicate in situ prior to step iii.) ofsaid process for dehydration of a mono-alcohol to obtain said catalyst.7. The process for dehydration of a mono-alcohol, or of a mixture of atleast two mono-alcohols, according to claim 1, wherein the productobtained after step c) is further shaped or extruded with a binderselected from AlPO₄, clay, zirconia, titania oxide or silica.
 8. Theprocess for dehydration of a mono-alcohol, or of a mixture of at leasttwo mono-alcohols, according to claim 5, characterized in that thebinder is selected to comprise: at least 85 wt % of silica as based onthe total weight of the binder; and/or less than 1000 ppm by weight asbased on the total weight of the binder of aluminium, gallium, boron,iron and/or chromium.
 9. The process for dehydration of a mono-alcohol,or of a mixture of at least two mono-alcohols, according to claim 1,wherein neither any steaming at a temperature higher than 380° C. norany leaching has been performed on said crystalline aluminosilicateprior to step a) and wherein neither any steaming at a temperaturehigher than 380° C. nor any leaching is further performed on saidmodified aluminosilicate after step c).
 10. The process for dehydrationof a mono-alcohol, or of a mixture of at least two mono-alcohols,according to claim 1, characterized in that said modified crystallinealuminosilicate has an acidity between 350 and 450 μmol/g measured bytemperature programmed desorption of ammonia.
 11. The process fordehydration of a mono-alcohol, or of a mixture of at least twomono-alcohols, according to claim 1, characterized in that said modifiedcrystalline aluminosilicate has Si/Al framework molar ratio ranging from10 to
 65. 12. The process for dehydration of a mono-alcohol, or of amixture of at least two mono-alcohols, according to claim 1,characterized in that said modified crystalline aluminosilicate has acontent of transition metals or cations thereof lower than 1000 wt ppmmeasured by the method ASTM UOP961-12, said transition metals belongingto any of the columns 3 to 12 of the Periodic Table.
 13. The process fordehydration of a mono-alcohol, or of a mixture of at least twomono-alcohols, according to claim 1, characterized in that saidconditions effective to dehydrate said mono-alcohol into said olefinshaving the same number of carbons are any combinations of: adiabatic orisotherm operating conditions or any of intermediate conditions inbetween including partial heat compensation or intermediate re-heating;and/or a temperature ranging from 200° C. to 500° C.; and/or a pressureranging from 0.5 bar to 15 bars (50 kPa to 1.5 MPa); and/or a WHSVranging from 1 to 30 h⁻¹ wherein the WHSV represents the weight flowrate of said mono-alcohol at the inlet of the reactor divided by themass of the catalyst composition in said reactor; and/or said feed (A)having a partial pressure of alcohols from 0.1 to 15 bars absolute (0.01MPa to 1.5 MPa).
 14. The process for dehydration of a mono-alcohol, orof a mixture of at least two mono-alcohols, according to claim 1,characterized in that said mono-alcohol(s) has at least 4 carbon atomsand in that said dehydration of a mono-alcohol is performed togetherwith a skeletal isomerization.
 15. The process for dehydration of amono-alcohol, or of a mixture of at least two mono-alcohols, accordingto claim 14, characterized in that said mono-alcohol is isobutanol andin that said isobutanol is converted into n-butenes and isobutene.